Chain of Martian disasters: when NASA confused the metric system with the imperial system | Science

The 1990s were disastrous for Mars exploration projects. Of the seven attempts, only two were successful. The apparent ease with which the Vikings landed hid the reality: landing on the Red Planet turned out to be much more difficult than it seemed. During the first fifty years of exploration of Mars, almost half of the devices sent there crashed or stopped working.

In September 1992, NASA launched its Mars observera platform that would continue and expand the research conducted from the Viking orbiters. It was a newly developed apparatus, the first of its class, intended for planetary visits not only to Mars, but also, in the future, with the necessary adaptations, to Venus or Mercury.

It was built from the standard casing of conventional communications satellites. This seemed like a good idea from the point of view of using already proven developments, but it was not so. Some of its components, which worked well for weeks around the Earth, failed to withstand the rigors of a months-long journey into a much colder environment.

When Mars observer With only a few days left before reaching the target, he was given the order to put pressure on the tanks in preparation for the braking maneuver. It is not known exactly what happened. Suspicions point to a small leak of oxidizer (nitrogen tetroxide) in the valve. Although there was only a small amount of it during the eleven-month flight, the corrosive liquid accumulated in the pipes. When the second set of valves opened, it came into contact with fuel, causing an explosion. This is just one of several hypotheses, but the sudden failure of communication did not allow a final conclusion to be reached.

He was luckier Global Mars Exploreranother probe was launched four years later. After failure observer The idea of ​​having a ship type that could be used for all missions had already been abandoned. It was a new design specifically designed for work on Mars; The scientific instruments he carried were almost identical to those lost in the previous attempt.

The relative positions of Earth and Mars made the journey long: eleven months. The culmination of the journey was the entry into a very elongated orbit, the altitude of which would decrease until it became circular at just 230 kilometers. The adjustment took another year and a half, since for the first time solar panels were used as an air brake instead of a chemical engine. They featured two adjustable fins and were strong enough to withstand the friction of the upper atmosphere repeatedly.

In the end, Global Surveyor It remained in a sun-synchronous orbit, designed to pass over the same terrain feature at the same solar time. The lighting conditions were the same, and the shadows, always the same, made it easy to detect changes in the landscape.

Although the projected useful life is only two years, M.G.S. His mission was repeatedly extended (that is, budgetary allocations were made), which allowed him to remain active for almost ten years. More than any other spacecraft sent to Mars so far. During this time, it received a quarter of a million images, as well as detailed altimetry coverage of the planet. This information will be of great help in preparing future operations of mobile robots that are about to arrive.

In November 1996, the Soviet Union ceased to exist. He Mars 8 It was to be the first deep space probe to fly the Russian tricolor flag, and was charged with an ambitious scientific program. In addition to a platform with video cameras and remote sensors, it carried two landing capsules and two penetrators. The latter is a type of dart two meters long that will be launched from orbit and plunged into the ground. Shortly before impact, they split into two parts: the warhead was deeply buried; the stern one, connected by a series of cables, will remain on the surface. The bow contained a seismometer, thermometers and mineralogical analyzers capable of withstanding an accident at a speed of 300 km/h; Its measurements will be sent to the orbiter through an emitter mounted at the back of the probe.

None of these plans could be realized. The rocket’s final stage failed and the probe, after spending a day in an irregular orbit around the Earth, disintegrated upon re-entry.

The losing streak continued, this time under the Japanese flag. Nozomi It was a small machine, which was equipped by four other foreign agencies. Its goal was also to fly around Mars to analyze its terrain, atmosphere and neighboring interplanetary environment.

The newest thing was his career. To achieve escape velocity without wasting much fuel, it was forced to pass close to the Moon twice and close to the Earth itself again, accelerating even further due to the gravitational pull. This maneuver cost him six months of sailing, but was successful. At the end of December 1998, with a little help from the engine, it set off for Mars.

Unfortunately, another poorly closed valve will waste valuable fuel needed to make the final course correction. Japanese specialists were forced to recalculate the trajectory in order to accelerate it without wasting fuel. It passed in front of the Earth twice more, but each maneuver meant another revolution around the Sun.

Odyssey A solar flare damaged communications equipment and the heater control system. The remaining hydrazine in the supply lines froze, and only by properly controlling the ship’s orientation and using the sun’s heat were they able to turn it back into liquid.

Finally, in December 2003, after five and a half years of travel, he almost reached his destination. Five more days and he would fire the maneuvering engine, forcing it to be captured. That’s when telemetry showed the launch vehicle was unresponsive and heading straight for Mars. Nozomi It was not sterilized before takeoff and therefore could not crash due to the risk of possible biological contamination. An order was hastily sent to fire up much weaker attitude control reactors to change its trajectory.

Nozomi It flew over Mars at an altitude of thousands of kilometers before getting lost in space.

But of all the failures of Mars exploration, few are as humiliating as the failure Mars Climate Orbiterlaunched by NASA in December 1998. Meteorological mission complementing a successful one Global Mars Explorer who continued to send photographs and measurements of excellent quality.

This time the goal was to study the evolution of the atmosphere of Mars over a couple of years. In particular, the abundance and distribution of water vapor, temperature and suspended dust are responsible for the characteristic pink color of the sky that the Vikings had already discovered.

During the nine-month journey, the trajectory seemed normal. Indeed, some slight deviations were noticed, but this is normal and can be corrected with the help of a shunting motor. In fact, four adjustments were made, so when the probe disappeared behind the planet to perform the capture operation in automatic mode, almost all the controllers and flight directors were calm. Almost. Not all.

He Climate Orbiter He never appeared again and was never heard from again. Subsequent analysis of the trajectory showed that instead of passing at an altitude of 150 kilometers, it passed at an altitude of less than 60. At this level, the atmosphere was already so dense that air friction was equivalent to the action of a blowtorch flame against a car. Perhaps it was burned; perhaps the sudden deceleration destroyed its structure before it even reached the ground; or the hydrazine in the tank has reached the flash point and exploded like a bomb. Or all three things at once.

Dejection gave way to chatter when the cause of the fatal deviation of the trajectory became known. Lockheed, the vehicle’s manufacturer, provided NASA’s Jet Propulsion Laboratory (JPL) with tracking data in the imperial dimensions common in the aviation industry; JPL has always worked in metrics. Pounds vs Newtons. And no one discovered this in time.

General shock after failure Climate Orbiter The situation was aggravated by the fact that there was another similar ship on the way. It was him Mars Polar Landerlander belonging to the same Mars exploration program.

NASA’s traditional caution of ensuring one step before taking the next was replaced by a more aggressive ideology and less concern about covering all eventualities. The agency manager’s new mantra was: “Faster, better, cheaper.” Many believed that the changes were for the worse, and ironically concluded the slogan with the words “…pick two.”

Investigation after the disaster Climate Orbiter He pointed to glaring cases of poor organization, lack of training, difficulties with communication between companies and even ignorance of how some systems work.

He Polar lander It was designed using much the same criteria: use simplified methods, reduce costs, limit testing… But its mission was complex: land near the Antarctic cap (about 75° south latitude), collect samples using a robotic arm and send them to analysis, photograph the area, measure a number of meteorological parameters (pressure, temperature, wind speed), determine the location of suspended ice in the lower layers of the atmosphere, and even detach a couple of capsules with instruments that need to be driven into frozen soil to study its characteristics.

None of this will happen. Although everything supposedly went well for most of the descent, the car never reacted. The most reasonable option is for it to fail. It was not possible to confirm this, since it did not transmit telemetry during the landing maneuver. Later attempts to photograph it from orbit still revealed a discarded parachute, but no sign of a lander.

Analysis of the malfunction indicated a possible culprit. When the landing gear was released at an altitude of 40 meters, vibration could cause a false signal, which the computer interpreted as contact with the ground. Consequently, this would stop the deceleration motor, allowing the polar lander to continue its free fall. The impact was too severe for such a fragile vehicle to survive.